Compounds having a fluorene backbone such as 9,9-bis(4-hydroxyphenyl) fluorine, etc. show features of high refractive index and low double refraction, and thus they are expected to be used in application as optical material, etc. Such a compound having a fluorene backbone is concretely used as a polymerization component (diol component, etc.), and considered to be used by incorporating it directly into a polymer backbone, or adding it to a resin as an additive, or the like.
A fluorene polyester oligomer prepared by polymerizing, as starting materials, a diol having a fluorene backbone and a dicarboxylic dihalide has been conventionally disclosed (for instance, Japanese Patent No. 5466927). This prior art, however, discloses a preparation method by reacting a diol having a fluorene backbone and a dicarboxylic dihalide only.
Accordingly, it is required to develop a novel polycarbonate copolymer having good transmittance due to the feature of low double refraction and having good impact strength at the same time, and a method for preparing the same.